Heat a sizable saucepan over medium heat and add the oil.
Sauté the onion, garlic, and ginger in the oil until fragrant.
Add the salt, broth, tomato paste, vinegar, and fish sauce to the saucepan, stirring well to combine.
Once the broth is blended, lower the heat, and add the long beans, eggplant, and tomatoes. Cover the pot and allow the vegetables to boil until they are almost cooked, stirring occasionally.
Add the shrimp and bitter melon, and simmer until the shrimp turns pink.
Taste and add more salt or fish sauce as needed.
Stir in the roast pork and cook thoroughly. To keep the pork crispy, shake the pot instead of stirring.